Research On Ceramic Coating Seal Valve Applied Technology

The spherical cone sealing structure is widely used in aerospace and chemical industry,research and improvement on its sealing performance have certain applying worth inengineering. This structure in filling tube connector is the crucial component for injectingpropellant. The connector presently used is typically made of1Cr18Ni9Ti, and it hasundergone pickling processes to increase the surface finish and the anti-oxidant capacity;however, it has not been subjected to special heat treatment. The majority of it used at presentare designed for single use; as such, they are unable to meet the possibility of the propellantbeing damaged several times. If the filling tube connector does not comply with the stricttightening torque standards, its sealing performance will reduce after reuse. Further, as theconnector is both made of stainless steel, when being used in space, the contact surface isprone to cold welding, which leads to sealing failure.To solve the above problem, experiments were conducted to study the sealingperformance of the filling tube connector, such as applying ceramic coating, heat treatment,and tightening torque management, and the best method is determined in the process. Thestress distribution of contact surface is simulated by the FEM software ANSYS. Besides this,an electron microscope was used to observe the spherical surface of a leaky filling tubeconnector to get the failure mechanism.Through the experimental study, we have found the best form of a filling tube connector,which is a model with titanium nitride coating connection and a plug that has undergone heattreatment. This form, applied with tightening torque management, has the best sealingperformance. The results of finite element simulation indicates that the maximum stressdecreases with the increasing thickness of coating, and the minimum occurs when the elasticmodulus of the matrix is similar to that of the coating. The results of the electron microscopeanalysis shows that the failure of the original and heat treatment filling tube connector ismainly due to debris abrasion and adhesion abrasion, and that of connector with coatingoccurs primarily due to the brittle spalling and furrows on the coating.